Would be interested to know how they got this effect. It looks like the blue has exploded and pushed itself into bits and the clear has moved in to fill up the gaps. It is smooth on the inside and textured on the outside - not sharp - very smoothly textured.

The effect is achieved by plunging the semi-blown hot gather of glass into cold water - the outside of the glass cracks. It is quickly removed, then reheated and reblown, to stretch out the cracks which appeared on the surface.The Ysarts used this technique in their "Cloissonne" bits, Michael Harris used it to make his "Crizzle" design. WMF used it in their Ikora ranges. It has been a popular technique for a long time.I've been told the official name for the process is actually "primavera".